/* xf86drmHash.c -- Small hash table support for integer -> integer mapping
* Created: Sun Apr 18 09:35:45 1999 by faith@precisioninsight.com
*
* Copyright 1999 Precision Insight, Inc., Cedar Park, Texas.
* All Rights Reserved.
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice (including the next
* paragraph) shall be included in all copies or substantial portions of the
* Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* PRECISION INSIGHT AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
* OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
* ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
* DEALINGS IN THE SOFTWARE.
*
* Authors: Rickard E. (Rik) Faith <faith@valinux.com>
*
* DESCRIPTION
*
* This file contains a straightforward implementation of a fixed-sized
* hash table using self-organizing linked lists [Knuth73, pp. 398-399] for
* collision resolution. There are two potentially interesting things
* about this implementation:
*
* 1) The table is power-of-two sized. Prime sized tables are more
* traditional, but do not have a significant advantage over power-of-two
* sized table, especially when double hashing is not used for collision
* resolution.
*
* 2) The hash computation uses a table of random integers [Hanson97,
* pp. 39-41].
*
* FUTURE ENHANCEMENTS
*
* With a table size of 512, the current implementation is sufficient for a
* few hundred keys. Since this is well above the expected size of the
* tables for which this implementation was designed, the implementation of
* dynamic hash tables was postponed until the need arises. A common (and
* naive) approach to dynamic hash table implementation simply creates a
* new hash table when necessary, rehashes all the data into the new table,
* and destroys the old table. The approach in [Larson88] is superior in
* two ways: 1) only a portion of the table is expanded when needed,
* distributing the expansion cost over several insertions, and 2) portions
* of the table can be locked, enabling a scalable thread-safe
* implementation.
*
* REFERENCES
*
* [Hanson97] David R. Hanson. C Interfaces and Implementations:
* Techniques for Creating Reusable Software. Reading, Massachusetts:
* Addison-Wesley, 1997.
*
* [Knuth73] Donald E. Knuth. The Art of Computer Programming. Volume 3:
* Sorting and Searching. Reading, Massachusetts: Addison-Wesley, 1973.
*
* [Larson88] Per-Ake Larson. "Dynamic Hash Tables". CACM 31(4), April
* 1988, pp. 446-457.
*
*/
#include <stdio.h>
#include <stdlib.h>
#include "xf86drm.h"
#include "xf86drmHash.h"
#define DIST_LIMIT 10
static int dist[DIST_LIMIT];
static void clear_dist(void) {
int i;
for (i = 0; i < DIST_LIMIT; i++)
dist[i] = 0;
}
static int count_entries(HashBucketPtr bucket)
{
int count = 0;
for (; bucket; bucket = bucket->next)
++count;
return count;
}
static void update_dist(int count)
{
if (count >= DIST_LIMIT)
++dist[DIST_LIMIT-1];
else
++dist[count];
}
static void compute_dist(HashTablePtr table)
{
int i;
HashBucketPtr bucket;
printf("Entries = %ld, hits = %ld, partials = %ld, misses = %ld\n",
table->entries, table->hits, table->partials, table->misses);
clear_dist();
for (i = 0; i < HASH_SIZE; i++) {
bucket = table->buckets[i];
update_dist(count_entries(bucket));
}
for (i = 0; i < DIST_LIMIT; i++) {
if (i != DIST_LIMIT-1)
printf("%5d %10d\n", i, dist[i]);
else
printf("other %10d\n", dist[i]);
}
}
static int check_table(HashTablePtr table,
unsigned long key, void * value)
{
void *retval;
int retcode = drmHashLookup(table, key, &retval);
switch (retcode) {
case -1:
printf("Bad magic = 0x%08lx:"
" key = %lu, expected = %p, returned = %p\n",
table->magic, key, value, retval);
break;
case 1:
printf("Not found: key = %lu, expected = %p, returned = %p\n",
key, value, retval);
break;
case 0:
if (value != retval) {
printf("Bad value: key = %lu, expected = %p, returned = %p\n",
key, value, retval);
retcode = -1;
}
break;
default:
printf("Bad retcode = %d: key = %lu, expected = %p, returned = %p\n",
retcode, key, value, retval);
break;
}
return retcode;
}
int main(void)
{
HashTablePtr table;
unsigned long i;
int ret = 0;
printf("\n***** 256 consecutive integers ****\n");
table = drmHashCreate();
for (i = 0; i < 256; i++)
drmHashInsert(table, i, (void *)(i << 16 | i));
for (i = 0; i < 256; i++)
ret |= check_table(table, i, (void *)(i << 16 | i));
compute_dist(table);
drmHashDestroy(table);
printf("\n***** 1024 consecutive integers ****\n");
table = drmHashCreate();
for (i = 0; i < 1024; i++)
drmHashInsert(table, i, (void *)(i << 16 | i));
for (i = 0; i < 1024; i++)
ret |= check_table(table, i, (void *)(i << 16 | i));
compute_dist(table);
drmHashDestroy(table);
printf("\n***** 1024 consecutive page addresses (4k pages) ****\n");
table = drmHashCreate();
for (i = 0; i < 1024; i++)
drmHashInsert(table, i*4096, (void *)(i << 16 | i));
for (i = 0; i < 1024; i++)
ret |= check_table(table, i*4096, (void *)(i << 16 | i));
compute_dist(table);
drmHashDestroy(table);
printf("\n***** 1024 random integers ****\n");
table = drmHashCreate();
srandom(0xbeefbeef);
for (i = 0; i < 1024; i++)
drmHashInsert(table, random(), (void *)(i << 16 | i));
srandom(0xbeefbeef);
for (i = 0; i < 1024; i++)
ret |= check_table(table, random(), (void *)(i << 16 | i));
srandom(0xbeefbeef);
for (i = 0; i < 1024; i++)
ret |= check_table(table, random(), (void *)(i << 16 | i));
compute_dist(table);
drmHashDestroy(table);
printf("\n***** 5000 random integers ****\n");
table = drmHashCreate();
srandom(0xbeefbeef);
for (i = 0; i < 5000; i++)
drmHashInsert(table, random(), (void *)(i << 16 | i));
srandom(0xbeefbeef);
for (i = 0; i < 5000; i++)
ret |= check_table(table, random(), (void *)(i << 16 | i));
srandom(0xbeefbeef);
for (i = 0; i < 5000; i++)
ret |= check_table(table, random(), (void *)(i << 16 | i));
compute_dist(table);
drmHashDestroy(table);
return ret;
}
